Pope Benedict XVI stunned cardinals Monday by announcing he is no longer able to fulfill his duties as head of the Catholic church due to age and failing health, and is stepping down at the end of the month.
Benedict delivered the news at the Vatican, speaking in Latin.
"After having repeatedly examined my conscience before God, I have come to the certainty that my strengths due to an advanced age are no longer suited to an adequate exercise of the Petrine ministry," the 85-year-old pope told the cardinals.
"In order to govern the bark of St. Peter and proclaim the Gospel, both strength of mind and body are necessary -- strengths which in the last few months, have deteriorated in me to the extent that I have had to recognize my incapacity to adequately fulfill the ministry entrusted to me.
Benedict said Feb. 28 will be his last day on the job.
The decision marks the first time in nearly 600 years that a sitting pontiff has left his position voluntarily. The last pope to resign voluntarily was Pope Gregory XII, in 1415. Gregory stepped down to deal with the Great Western Schism among competing papal claimants. Prior to that, Pope Benedict IX resigned from the post in 1045.
Benedict's decision sets the stage for a conclave to elect a new pope before the end of March, and opens the door to widespread speculation among Roman Catholics about his possible successor.
Cardinal Angelo Scola, archbishop of Milan, Cardinal Christoph Schoenborn, the archbishop of Vienna, and Cardinal Marc Ouellet, the Canadian head of the Vatican's office for bishops are considered among the top candidates for the job.
Toronto's archbishop, Cardinal Thomas Collins, said he was stunned by the news Monday morning and hasn't even begun to think about a possible successor.
"It is a time to thank God for (Benedict's) mission amongst us and to pray for him in the years ahead as he enters into this new time," Collins told reporters in Toronto. "As he said he will spend the rest of his life in prayer, no longer having the heavy responsibilities as the Vicar of Christ on Earth and as the successor to Saint Peter."
Collins, who was installed as a cardinal in 2012, will be among those voting for Benedict's replacement during the process known as a conclave. He said no timeline has yet been set, but the process will likely begin immediately after Benedict's term ends at 8 p.m. on Feb. 28.
All cardinals will meet and discuss the needs of the church for several days. Those who are under 80 will then go behind closed doors to vote for the next pope, a process that could take days.
"I think the whole church gathers together at such a time in prayer for the College of Cardinals and this most profound mission we have, which is to elect the successor to (Saint) Peter," Collins said.
Vatican in shock
The Vatican stressed Monday there is no specific medical condition that affected Benedict’s decision.
Benedict's 89-year-old brother, Georg Ratzinger, said doctors had recently advised the Pope not to take any more trans-Atlantic trips, and he had slowed down considerably.
"His age is weighing on him," Ratzinger told the dpa news agency. "At this age my brother wants more rest."
Still, the news was so unexpected that several cardinals on Monday didn't even understand what Benedict had said when he made the announcement in Latin. Those who did were stunned.
"All the cardinals remained shocked and were looking at each other," said Monsignor Oscar Sanchez of Mexico, who was in the room when Benedict made his announcement.
In 2010, in an interview for the book "Light of the World," Benedict raised the possibility of resigning if he were simply too old or sick to continue on.
"If a pope clearly realizes that he is no longer physically, psychologically and spiritually capable of handling the duties of his office, then he has a right, and under some circumstances, also an obligation to resign," Benedict said at the time.
Rise to papacy
Benedict – formerly known as Cardinal Joseph Ratzinger -- was elected pope on April 19, 2005 in one of the fastest conclaves in modern history. He reportedly was elected after four ballots, with 84 of 115 votes.
He had spent his life working in the Catholic church. Born in 1927 in Germany, Ratzinger wrote in his autobiography that he considered the church and Catholic seminary where he studied to be a "citadel of truth and righteousness against the realm of atheism and deceit."
Though he joined the Hitler Youth movement at 14, when it became mandatory in Germany to do so, he said he shared his father's opposition to Nazi ideals.
As a young man, he was eventually conscripted into the German military in 1943. He later deserted and became a prisoner of war in the custody of the Americans.
After the Second World War he returned to Munich, completed his studies and was ordained as a priest in 1951. From there, Benedict went on to graduate studies, a professorship, and the work within the church that would eventually see him rise to the ranks of archbishop, cardinal and finally pope in 2005.
In one of his more influential moves after assuming office, Benedict changed the rules for electing a new pope in 2007, reversing reforms made by Pope John Paul in 1996.
Benedict's predecessor altered the process so that an absolute majority of cardinals could choose the new pope in the event they were unable to reach a two-thirds majority after several days of balloting.
Benedict returned to the traditional method, whereby a new pope can only be elected by a minimum two-thirds majority of cardinals, regardless of how long it takes.